• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.28-35
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• 2002

In cavity flow, the rectangular step generates so strong sound that many researchers have investigated method to suppress the nois during interaction between vortical flow and rectangular forward step. In this study the flow noise from the vortex motion in two-dimentional low Mach number flow past a forward step with various chamfering angle is calculated numerically. Inviscid incompressible discrete vortex model and matched asymptotic expansion(MAE) theory are applied to obtain the inner flow field and the outer noise field. Both source acoustic pressure and sound intensity are obtained with various chamfering height, chamfering angle and initial vortex position. The pressure amplitude is most suppressed when the chamfering angle is between $15^{\circ}C$ and $30^{\circC}$ at the chamfering length of 30% of the step height.

• Convergence Security Journal
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• v.16 no.4
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• pp.25-34
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• 2016

This paper shall suggest the improvement model for invigorating cyber threat information sharing from the national level, which includes, inter alia, a comprehensive solutions such as the legislation of a guideline for information sharing, the establishment of so-called National Center for Information Sharing, the construction and management of a integrated information system, the development of techniques for automatizing all the processes for gathering, analyzing and delivering cyber threat information, and the constitution of a private and public joint committee for sharing information, so much so that it intends to prevent cyber security threat to occur in advance or to refrain damage from being proliferated even after the occurrence of incidents.

• Journal of the Korea Institute of Building Construction
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• v.20 no.4
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• pp.339-345
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• 2020

This study used a real-scale model experiment to reproduce internal fires in residential buildings such as a multi-dwelling unit, in order to prevent damage caused by tens of thousands of fires witnessed each year and to take measures to cope with them. For experimental conditions, different opening sizes were applied to measure and analyze the heating temperature of the exterior wall. Results drawn are as follow : On top of this, the experimental conditions had whether to install shading and put a shading length differently, before measuring and analyzing the heating temperature of the exterior wall. Subsequent results were drawn as shown below. Based on the maximum temperature, the temperature was lowered as much as around 90℃ at 150mm, around 150℃ or over at 300mm and over 175℃ at 450mm. It also turned out that the difference in maximum temperature dropped by around 180℃ or over. This indicated that the shading installation works well in lowering flame temperature generated by fire spread of the exterior wall.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.13-22
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• 2004

In case of the lateral movement accurring at soft ground where a row of piles are installed, the crown failure at external arch zone of soil arching is firstly developed, and the cap failure at wedge zone in front of piles is lastly developed. Therefore, the lateral earth pressure acting on a row of piles due to soil movement should be calculated in each condition of crown and cap failures around piles. A theoretical equation of crown failure can be proposed using a cylindrical cavity expansion theory. The theoretical equation of crown failure is mainly affected by two factors. One is related to soil properties such as internal friction angle, cohesion and horizontal pressure, and the other is related to pile factors such as diameter, installation interval. Meanwhile, the yield range of lateral earth pressure is established in the estimation of theoretical equation based on crown and cap failures around piles. The theoretical values based on crown and cap failures are compared with the experimental values. The experimental values are located in the range proposed by theoretical values. Thus, it is confirmed that the theoretical values proposed in the study are very reasonable.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.4
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• pp.709-719
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• 2015

This paper introduces a proper renaming service using variable action and security services against the analysis techniques in Java code. The renaming service that is introduced is separated into API pattern and loop condition. We present our scheme algorithm with known Java obfuscation techniques and tools in order to help readers understanding, and implement prototype to prove practicality in this paper. Test result using prototype shows 73% successful variable renaming rate. Using our scheme, cooperators can intuitionally understand all of code. Also, It helps malware analysts to predict malware action by variable name. But application source code that is developed by Java is exposed to hackers easily using our scheme. So we introduce Java application code protection methods, too.

• Journal of the Economic Geographical Society of Korea
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• v.15 no.2
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• pp.292-303
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• 2012

The main purpose of this study is to analyze R&D networks and spatial implications in Qingdao consumer electronics industry agglomeration in China. The characteristics of R&D networks in Qindao consumer electronic industry are as follows. There is a cluster central around large enterprises led by the government and their subcontracting enterprises. However, the degree of collaborative networks in intra-firm, inter-firm, firm-research institutes(including university lab.) is relatively low. Therefore, Large enterprises in Qingdao has stimulated research collaborations with firms and research institutes located in other regions rather than within region. It is likely to show that R&D networks of consumer electronics industry has not been stimulated in Qingdao. Therefore, collaborative R&D networks among firms, research institutes and governments should be stimulated to build regional innovation systems central around consumer electronics industry in Qingdao.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.81-86
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• 2007

The air velocity flowing in inner combustion chamber of Scramjet is supersonic and the time of its stay is very short as a few milliseconds. Within this short time, fuel injection, air-fuel mixing, and combustion process should be accomplished. Several methods are suggested for mixing enhancement. Among these, cavity is selected to study for enhancement of mixing. The numerical simulation is performed in the case of freestream Mach number of 2.5 and cavity located in front of fuel jet injection. 8 different sized cavities of length-height ratio were used in order to recognize the effect about cavity size. Also, the case without cavity was analyzed to find the effect of cavity. Used code compared with the result of experiment under identical conditions and it was verified. Through this comparison and verification, mixing enhancement by cavity could be confirmed.

• Fire Science and Engineering
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• v.30 no.5
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• pp.144-150
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• 2016

An apartment house with a pilotis that raises the architectural volume and provides a space for circulation is becoming popular. With the popularity of pilotis in apartment houses, people also have a keen interest in the potential fire risk at the pilotis. As residents can only access their apartment house through the pilotis, there is a risk to the occupants if there is fire there. Therefore, this study evaluated the pilotis fire cases of urban multifamily housing to conduct a Fire Dynamics Simulator (FDS) and Fire Evacuation Simulation (FES). Through these two simulation methods, it is possible to validate the riskiness of fire at an apartment with a pilotis. The study identified that the toxic gases and flame spread out to the pilotis within hundred seconds after ignition. In addition, the toxic gases and flame also reach the second floor within three seconds and the entire building within 735 seconds if the entrance doors at the pilotis are opened. On the other hand, the FES simulation results showed that it also takes about approximately 609 seconds to excavate from the apartment house with a pilotis. Therefore, this research shows that an apartment house with a pilotis can ensure the building occupants' lives and their safety if there is fire.

• Journal of the Korean association of regional geographers
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• v.10 no.4
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• pp.713-726
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• 2004

This paper aims to investigate the characteristics of innovation activities and informal networks of venture companies in Daegu region. The most important knowledge source of them for innovation is in house. The next are customers, competitors, and public supporters. And it was investigated that regional venture companies have participated in 1-5 informal network organizations. They primarily achieve such knowledges as, technologies, new business opportunities, and marketing information, through participation in informal networks. The reasons why they have taken part in informal networks are to get new informations and acquire new business opportunities. Particularly The informal networks between ventures companies and other regional economic actors have helped the regional venture companies to obtain more economic performance and to establish social capital, such as faith, with other economic actors.

• Journal of the Korean Geographical Society
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• v.51 no.6
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• pp.819-836
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• 2016

The development paradigm based on modernization theory and economic growth since the WWII reached an impasse in the 1980s. As an alternative, the new perspective on development as a whole social development beyond economic growth has emerged, and culture as an important method for as well as a approach to development has been emphasized. Post-development theories destruct the European development concept and suggest alternative developments emphasizing culture restoration, endogenous growth, diversity, and neopopulist developments movement emphasize community, gender, ownership, and participation. International Organizations such as UNESCO have also examined and developed the relations between culture and development. Although different from that of the past development paradigm, acknowledging other cultures, however, this elaborated concept of culture has some limitations and need to be reconceptualized through applying the geographical concept of 'relational place.' The concept of relational place can help recognize internal diversity within culture and community and link them to a broader economic and political contexts.